Method of recovering oil using a chemical blending system

ABSTRACT

This specification discloses a system and method for blending a dry chemical and a liquid. A particular application of this invention is in polymer waterflooding an oil-containing subterranean formation to recover oil therefrom. A dry polymer and a liquid are blended to form a viscous liquid which is used in the polymer waterflooding operation. The system is comprised of a hopper for receiving and feeding the dry chemical into a pipe where it is transported by gas to a liquid weir and there mixed with the liquid. The hopper is adapted for having a positive pneumatic pressure applied at an upper location thereof and a negative pneumatic pressure applied at a lower location thereof to feed the dry chemical into a pipe. The dry chemical is then transported by gas through the pipe and directed from the downstream end of the pipe into the liquid weir. The liquid weir is adapted for having liquid flowed therethrough to mix and blend the liquid with the dry chemical. A container is provided to contain the blended mixture.

United States Patent [19] Watson, Jr.

Sept. 2, 1975 [75] Inventor: Wilson D. Watson, Jr., Midland,

Tex.

['73] Assignee: Mobil Oil Corporation, New York,

[22] Filed: Dec. 20, 1973 [21] Appl. No.: 426,843

[52] US. Cl 166/305 R; 166/275; 166/75; 259/4; 259/18 [51] Int. Cl. E21B 43/22 [58] Field of Search 259/4, 18, 36, DIG. l7; 166/273-275, 75, 268, 305 R [56] References Cited UNITED STATES PATENTS 3,039,529 6/1962 McKennon 166/275 3,338,560 8/1967 Katzer et a1. 259/4 3,425,669 2/1969 Gaddis 259/18 3,752,446 8/1973 Watanabe.... 259/4 X 3,8l9,l57 6/1974 Markfelt 259/4 3,825,067 7/1974 Vestal 166/275 Primary Examiner--Stephen J. Novosad Attorney, Agent, or Firm-C. A. Huggett; Henry L. Ehrlich [57] ABSTRACT This specification discloses a system and method for blending a dry chemical and a liquid. A particular application of this invention is in polymer waterflooding an oil-containing subterranean formation to recover oil therefrom. A dry polymer and a liquid are blended to form a viscous liquid which is used in the polymer waterflooding operation. The system is comprised of a hopper for receiving and feeding the dry chemical into a pipe where it is transported by gas to a liquid weir and there mixed with the liquid. The hopper is adapted for having a positive pneumatic pressure applied at an upper location thereof and a negative pneumatic pressure applied at a lower location thereof to feed the dry chemical into a pipe. The dry chemical is then transported by gas through the pipe and directed from the downstream end of the pipe into the liquid weir. The liquid weir is adapted for having liquid flowed therethrough to mix and blend the liquid with the dry chemical. A container is provided to contain the blended mixture.

4 Claims, 3 Drawing Figures PATENTEUSEP 21975 3,902,558

sum 1 OF 3 FIG. I

METHOD OF RECOVERING OIL USING A CHEMICAL BLENDING SYSTEM SUMMARY OF THE INVENTION This invention is directed to a system for blending a dry chemical and a liquid. This system is comprised of a hopper which is adapted for receiving and feeding the dry chemical. The hopper is adapted for having a positive pneumatic pressure applied at an upper location thereof and for maintaining therein the positive pneumatic pressure. There is connected to the lower end of the hopper a means for applying a negative pneumatic pressure thereto and for feeding the dry chemical into a pipe. A means is provided for supplying gas under pressure to an upstream end of the pipe to transport the dry chemical through the pipe and discharge the dry chemical and gas into a liquid weir. There is provided a means for supplying liquid to the liquid weir such that the dry chemical and liquid are blended. A container is provided for containing the blended dry chemical and liquid.

An embodiment of this invention is directed to a method of recovering oil from an oil-containing subterranean formation wherein a polymer solution is injected via an injection well into the formation and more particularly to a method of blending a dry polymer and water to form the polymer solution. Gas is injected via an upper location into a hopper having dry polymer therein to apply and maintain a positive gas pressure above the polymer. Gas is flowed through a pipe and polymer is flowed from the lower end of the hopper into the pipe. The polymer is transported by the gas to a downstream end of the pipe and discharged into a water weir. concomitantly, water is supplied to the water weir to form a sheet of water and to mix the polymer with the water and form a polymer solution.

BACKGROUND OF THE INVENTION This invention is directed to a method of blending a dry chemical with a liquid.

It is desirable in many applications to mix or blend dry chemicals of the type which flow freely, e.g. powdery dry chemicals, with a liquid and form a blended mixture. An application where large volumes of dry chemicals are mixed or blended with a liquid is in the recovery of oil from an oil-containing subterranean formation wherein a viscous liquid is injected via an injection well into the oil-containing subterranean formation to assist in the recovery of oil therefrom. The viscous liquid may be a polymer solution formed by blending or mixing a dry polymer with an aqueous fluid. Examples of such polymers are partially hydrolyzed polyacrylamides which are sold by Calgon Corporation under the trade name ofCalgon 454 and polysaccharides which are sold by Kelco Corporation under the trade name of Kelzan. These polymers, as well as many other dry chemicals, are soluble in a liquid, but have a tendency to polymerize, gum or ball-up when brought into contact with the solubilizing liquid. Furthermore, this tendency presents problems due to, the

humidity naturally present in the air when using equipment such as hoppers and associated equipment for feeding and blending the polymers and dry chemicals with a solubilizing liquid. In the case of hoppers it has been found that the polymers and dry chemicals do not fall freely therefrom. Vibrators and screw conveyors have been used in conjunction with hoppers to assist in feeding and conveying the polymers and dry chemicals from the hoppers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow sheet which illustrates schematically the system and method of this invention.

FIGS. 2A and 2B are isometric end views illustrating a liquid weir for blending a dry chemical with a liquid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with this invention there is provided a system and method for feeding and blending dry chemicals with a liquid.

This invention is applicable for blending liquid with a dry chemical of the type that may be flowed from a hopper. A particular application of this invention is in conjunction with polymer waterfloods that are carried out in the recovery of oil from oil-containing subterranean formations. Therefore, for illustrative purposes, this invention is described in its application to feeding and blending a polymer with water to form a viscous liquid for use in the recovery of oil from an oilcontaining subterranean formation.

Referring to FIG. 1 there is shown a flow sheet illus trating the system of this invention. A hopper 1 is shown for receiving dry polymer 3 from, for example, a polymer storage 5 via a conduit 7. The polymer 3 may be injected into the hopper 1 through an inlet 9. A valve 11 is provided in the conduit 7 for opening and closing the conduit 7. The lower part of the hopper 1 slopes inwardly toward the vertical axis of the hopper and an outlet port 13 is provided at the lower extremity thereof. A valve 15 is provided in a conduit 43 that connects the outlet port 13 with a conduit 19.

An air source 17 is provided which may be, for example, an air compressor. Air is flowed from the air source 17 through the conduit 19 to a water weir 21. A portion of the air flowing through the conduit 19 is flowed through a connecting conduit 35 and into an upper location of the hopper l. Preferably the air is treated to remove water vapor therefrom and to provide dry air for flowing into the upper location of the hopper 1 and for transporting the dry polymer 3 from the hopper 1 via conduit 19 to the water weir 21. The dry air may be provided by dehumidifying the air prior to its coming into contact with the polymer 3. A system is illustrated for dehumidifying the air which makes use of a watertype air cooler 23. The air is passed through the watertype air cooler 23 and water from a water source (not shown) is circulated via pipe 25 through the air cooler 23 and then is exhausted to a water storage or disposal system (not shown). The air is then flowed from the air cooler 23 via the conduit 19 to an air scrubber 24 to further dehumidify and clean the air and thence flowed through the conduit 19 to an air volume tank 27. A pipe 29 and automatic dump valve 31 are provided to exhaust the water removed from the air to the water disposal system. The air is flowed from the volume tank 27 via the conduit 19 to an air pressure regulator 32 to regulate the pressure as desired. The air stream flowing through the conduit 19 is split at point 33 and a first part of the air is flowed through the conduit 35 and through inlet 37 into the hopper 1 above the polymer 3 contained therein. A valve 39 may be provided in the conduit 35 for controlling the flow of the air therethrough. The air which flows through the conduit 35 and into the upper part of hopper 1 serves the purpose of providing a positive pneumatic pressure above the polymer 3 in hopper 1 and thus assists in forcing the polymer 3 to flow from the hopper 1 through the exit port 13 thereof. The use of dry air eliminates other problems which commonly occur in the blending of polymer with water such as polymerizing and gumming up of the polymer within the hopper 1 and, in particular, in the vicinity of the exit port 13 of hopper 1.

The second part of the air flows past point 33 toward the downstream end of the conduit 19. The exit port 13 of the hopper 1 is connected via the conduit 43 and the valve to the conduit 19. An induction valve 45 illustrated by the dashed rectangle is provided to connect the conduit 19 with the conduit 43 and to provide a suction pressure on exit port 13. This suction pressure is a pressure which is less than the pressure applied above the polymer 3 within hopper 1 and is hereafter referred to as a negative pressure. A negative pressure may be applied by other means than an induction valve,

for example, by connecting a vacuum pump to the exit port 13. However, an induction valve is a practical means of applying this negative pressure and is the preferred means for use in this system. The negative pressure which is applied to the exit port 13 works in conjunction with the positive pressure applied within the hopper 1 above the polymer 3 and with the force of gravity to cause the polymer 3 to flow downward through the exit port 13 and into the conduit 19 where it is entrained by the air flowing therein and is transported downstream through the conduit 19. The air and dry polymer exit at the downstream end of the conduit 19 into the water weir 21. Water from a water source (not shown) is flowed through a pipe 47 to the water weir 21. A meter 49 may be provided in the pipe 47 to meter the water flowing therethrough. The water weir 21 spreads the water into a sheet and allows it to fall into a tank 51. The polymer and air exiting from the downstream end of the conduit 19 are directed to this water weir where the polymer 3 is sprayed on the sheet of water to mix and blend with the water. A nozzle 85, FIG. 2, may be employed at the downstream end of the conduit 19 to better spray and direct the polymer onto the sheet of water formed by the water weir.

Referring to FIGS. 2A and 2B, there is shown isometric end views of the water weir 21. The pipe 47 connects with the water weir 21 and water in a metered amount is flowed through the pipe 47 and into the water weir 21. The water flows through the water weir 21 and over the edge 84 to form a sheet of water (not shown) which falls into and is contained by the tank 51 of FIG. 1. The air containing the entrained polymer flows from the conduit 19 and is directed into the sheet of water falling over the edge 84 of the water weir 21 where the polymer is readily blended with the water. Preferably a nozzle 85 is attached to the downstream end of the conduit 19 to spray the air and polymer into the sheet of water. Preferably the nozzle 85 is a type which directs the air and polymer exiting from the conduit 19 into a flat spray to better contact and blend the polymer with the water.

The blended aqueous mixture of polymer may then be transferred from the tank 51 via a pipe 53 and pump 55 to a holding tank 57. The blended solution of polytering the fluid transferred from the holding tank 57 into the suction tank 65. Fresh water from a water source (not shown) may be injected through a pipe 67, valve 69, and meter into the suction tank 65, and a mechanical blender 71 located therein may be used to further blend fresh water with the polymer solution, thus diluting the solution as desired.

In the embodiment directed to the recovery of oil from an oil-containing subterranean formation, the viscous liquid or polymer solution is injected via an injection well 77 and into the subterranean formation 79. The well 77 may be conventionally completed as an injection well. There is shown in the well 77 a casing 81 which extends to about the top of the formation 79 and is cemented in place by a cement sheath 83. A tubing string 86 may extend down the casing 81 and communicate with the formation 79. A packer 87 is shown isolating the lower end of the tubing string 85 from the interior of the casing 81. The polymer solution is transferred via a line 73 and injection pump to the well 77 and injected down the tubing 86 and into the subterraneon formation 79 and is driven therethrough to assist in the recovery of oil therefrom.

I claim:

1. In a method for the recovery of oil from an oilcontaining subterranean formation wherein a viscous liquid is injected via an injection well into said formation, the method of blending a dry polymer and a liquid to form said viscous liquid, comprising the steps of:

a. flowing water to form a free-falling sheet of water;

b. applying a positive pneumatic pressure to an upper location of a hopper having said dry polymer therein, said hopper being adapted for maintaining a positive pneumatic pressure therein;

0. applying a negative pneumatic pressure to the lower end of said hopper to feed said dry polymer into a conduit;

d. flowing gas through said conduit to transport said dry polymer therethrough; and

e. discharging said dry polymer and said gas from the downstream end of said conduit into said freefalling sheet of water to mix said water and said dry polymer and form said viscous liquid.

2. In a method of recovering oil from an oilcontaining subterranean formation wherein a polymer solution is injected via an injection well into said formation, the method of blending a dry polymer and water to form the polymer solution, comprising the steps of:

a. injecting gas via an upper location into a hopper having dry polymer therein and applying and maintaining a positive gas pressure above said polymer;

b. flowing gas through a conduit;

0. flowing said polymer from a lower end of said hopper into said conduit;

d. transporting said polymer with said gas to a downstream end of said conduit;

e. flowing water to form a free-falling sheet of water;

and

f. discharging said polymer and said gas from said conduit into said free-falling sheet of water to mix said polymer and water to form said polymer solution.

3. The method of claim 2 wherein said gas in step (a) and step (b) is dry gas.

4. The method of claim 3 wherein in step (c) a negative gas pressure is applied to said lower end of said hopper. 

1. IN A METHOD FOR THE RECOVERY OF OIL FROM AN OIL-CONTAINING SUBTERRANEAN FORMATION WHEREIN A VISCOUS LIQUID IS INJECTED VIA AN INJECTION WELL INTO SAID FORMATION, THE METHOD OF BLENDING A DRY POLYMER AND A LIQUID TO FORM SAID VISCOUS LIQUID, COMPRISING THE STEPS OF: A. FLOWING WATER TO FORM A FREE-FALLING SHEET OF WATER, B. APPLYING A POSITIVE PNEUMATIC PRESSURE TO AN UPPER LOCATION OF A HOPPER HAVING SAID DRY POLYMER THEREIN, SAID HOPPER BEING ADAPTED FOR MAINTAINING A POSITIVE PNEUMATIC PRESSURE THEREIN, C. APPLYING A NEGATIVE PNEUMATIC PRESSURE TO THE LOWER END OF SAID HOPPER TO FEED SAID DRY POLYMER INTO A CONDUIT, D. FLOWING GAS THROUGH SAID CONDUIT TO TRANSPORT SAID DRY POLYMER THERETHROUGH, AND E. DISCHARGING SAID DRY POLYMER AND SAID GAS FROM THE OWNSTREAM END OF SAID CONDUIT INTO SAID FREE-FALLING SHEET OF WATER TO MIX SAID WATER AND SAID DRY POLYMER AND FORM SAID VISCOUS LIQUID.
 2. In a method of recovering oil from an oil-containing subterranean formation wherein a polymer solution is injected via an injection well into said formation, the method of blending a dry polymer and water to form the polymer solution, comprising the steps of: a. injecting gas via an upper location into a hopper having dry polymer therein and applying and maintaining a positive gas pressure above said polymer; b. flowing gas through a conduit; c. flowing said polymer from a lower end of said hopper into said conduit; d. transporting said polymer with said gas to a downstream end of said conduit; e. flowing water to form a free-falling sheet of water; and f. discharging said polymer and said gas from said conduit into said free-falling sheet of water to mix said polymer and water to form said polymer solution.
 3. The method of claim 2 wherein said gas in step (a) and step (b) is dry gas.
 4. The method of claim 3 wherein in step (c) a negative gas pressure is applied to said lower end of said hopper. 